Filed by The Chubb Corporation

pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934

Subject Company: The Chubb Corporation

Commission File No.: 1-8661

Chubb disseminated the following ACE press release to its employees on July 27, 2015.

ACE Limited Bärengasse 32 CH-8001 Zurich Switzerland acegroup.com @ACEGroup

ACE Announces Paul Krump to Assume Future Executive Leadership Position for Global Underwriting and Claims for Parent Company

Appointment to become effective upon completion of ACE’s acquisition of Chubb

Zurich — July 27, 2015 — ACE Limited announced today that Paul Krump, currently President of Personal Lines and Claims for Chubb, will serve as Executive Vice President for Global Underwriting and Claims for the parent company. The intended appointment will take effect upon completion of the acquisition of Chubb, which is expected in the first quarter of next year.

Mr. Krump will provide counsel, assistance and direction to Frank Lattal, who is currently Chief Claims Officer for ACE Group and who will continue to serve in that role and report to Mr. Krump. Mr. Krump will also partner with Jacques Bonneau, who is Executive Vice President, Global Underwriting, ACE Group and who will continue to serve in that role to advance underwriting excellence across the organization. Mr. Krump will report to John Keogh, who is currently Vice Chairman and Chief Operating Officer of ACE Group and who will continue to serve in that role. In addition, Mr. Krump will join the parent company’s Executive Committee.

“I am pleased to announce our intention to appoint Paul to this senior corporate position where he will work closely with our many underwriting and claims executive colleagues around the globe,” said Evan G. Greenberg, Chairman and Chief Executive Officer of ACE. “Working with Frank, Paul will call upon his tremendous experience, including many years in general management, to bring together the strengths of both companies’ claims organizations. Paul is an underwriter’s underwriter and he will bring to bear his proven record and deep insights into risk and all facets of underwriting. After all, underwriting is the reason we exist as a company, and a well-run insurance company is an underwriting company.”

About ACE Group

ACE Group is one of the world’s largest multiline property and casualty insurers. With operations in 54 countries, ACE provides commercial and personal property and casualty insurance, personal accident and supplemental health insurance, reinsurance and life insurance to a diverse group of clients. ACE Limited, the parent company of ACE Group, is listed on the New York Stock Exchange (NYSE: ACE) and is a component of the S&P 500 index. Additional information can be found at: www.acegroup.com.

ACE^®, ACE logo^®, and ACE insured^® are trademarks of ACE Limited. 1

ACE LIMITED NEWS RELEASE

Contacts

Investors:

Helen Wilson: (441) 299-9283; helen.wilson@acegroup.com

Media:

Jeffrey Zack: (212) 827-4444; jeffrey.zack@acegroup.com

Cautionary Statement Regarding Forward-Looking Statements

All forward-looking statements made in this communication, related to the acquisition of Chubb, potential post-acquisition performance or otherwise, reflect ACE’s current views with respect to future events, business transactions and business performance and are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. In some cases, you can identify forward-looking statements by words such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “potential,” “continue,” “could,” “future,” “project” or other words of similar meaning. All forward-looking statements involve risks and uncertainties, which may cause actual results to differ, possibly materially, from those contained in the forward-looking statements.

Forward-looking statements include, but are not limited to, statements about the benefits of the proposed transaction involving ACE and Chubb, including future financial results; ACE’s and Chubb’s plans, objectives, expectations and intentions; the expected timing of completion of the transaction and other statements that are not historical facts. Important factors that could cause actual results to differ, possibly materially, from those indicated by the forward-looking statements include, without limitation, the following: the inability to complete the transaction in a timely manner; the inability to complete the transaction due to the failure of Chubb’s shareholders to adopt the transaction agreement or the failure of ACE shareholders to approve, among other matters, the issuance of ACE common shares in connection with the acquisition; the failure to satisfy other conditions to completion of the transaction, including receipt of required regulatory approvals; the failure of the proposed transaction to close for any other reason; the possibility that any of the anticipated benefits of the proposed transaction will not be realized; the risk that integration of Chubb’s operations with those of ACE will be materially delayed or will be more costly or difficult than expected; the challenges of integrating and retaining key employees; the effect of the announcement of the transaction on ACE’s, Chubb’s or the combined company’s respective business relationships, operating results and business generally; the possibility that the anticipated synergies and cost savings of the merger will not be realized, or will not be realized within the expected time period; the possibility that the transaction may be more expensive to complete than anticipated, including as a result of unexpected factors or events; diversion of management’s attention from ongoing business operations and opportunities; general competitive, economic, political and market conditions and fluctuations; and actions taken or conditions imposed by the United States and foreign governments and regulatory authorities. In addition, you should carefully consider the risks and uncertainties and other factors that may affect future results of the combined company described in the section entitled “Risk Factors” in the joint proxy statement/prospectus to be delivered to ACE’s and Chubb’s respective shareholders, and in ACE’s and Chubb’s respective filings with the Securities and Exchange Commission (“SEC”) that are available on the SEC’s website, located at www.sec.gov, including the sections entitled “Risk Factors” in ACE’s Annual Report on Form 10–K for the year ended December 31, 2014, which was filed with the SEC on February 27, 2015, and “Risk Factors” in Chubb’s Annual Report on Form 10–K for the year ended December 31, 2014, which was filed with the SEC on February 26, 2015. You should not place undue reliance on forward-looking statements, which speak only as of the date of this communication. ACE undertakes no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

ACE^®, ACE logo^®, and ACE insured^® are trademarks of ACE Limited. 2

ACE LIMITED NEWS RELEASE

Additional Information and Where to Find It

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. This communication may be deemed to be solicitation material in respect of the proposed transaction between ACE and Chubb. In connection with the proposed transaction, ACE intends to file a registration statement on Form S-4, containing a joint proxy statement/prospectus with the SEC. The final joint proxy statement/prospectus will be delivered to the shareholders of ACE and Chubb. This communication is not a substitute for the registration statement, definitive joint proxy statement/prospectus or any other documents that ACE or Chubb may file with the SEC or send to shareholders in connection with the proposed transaction. SHAREHOLDERS ARE URGED TO READ ALL RELEVANT DOCUMENTS FILED WITH THE SEC, INCLUDING THE JOINT PROXY STATEMENT/PROSPECTUS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.

Shareholders will be able to obtain copies of the joint proxy statement/prospectus and other documents filed with the SEC (when available) free of charge at the SEC’s website, http://www.sec.gov. Copies of documents filed with the SEC by ACE will be made available free of charge on ACE’s website at www.acegroup.com. Copies of documents filed with the SEC by Chubb will be made available free of charge on Chubb’s website at www.chubb.com.

Participants in Solicitation

ACE, Chubb and their respective directors, executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about the directors and executive officers of ACE is set forth in the proxy statement for ACE’s 2015 Annual General Meeting, which was filed with the SEC on April 8, 2015, and ACE’s Annual Report on Form 10-K for the year ended December 31, 2014, which was filed with the SEC on February 27, 2015. Information about the directors and executive officers of Chubb is set forth in the proxy statement for Chubb’s 2015 Annual Meeting of Shareholders, which was filed with the SEC on March 13, 2015, and Chubb’s Annual Report on Form 10-K for the year ended December 31, 2014, which was filed with the SEC on February 26, 2015. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the joint proxy statement/prospectus and other relevant materials filed with the SEC. You may obtain free copies of these documents as described above.

ACE^®, ACE logo^®, and ACE insured^® are trademarks of ACE Limited. 3